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Columbia 400 nose wheel shimmy


CAV Ice

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Have a Columbia 400 with a nose wheel shimmy. It is very light below 20kts and increases to moderate between 25 and 28kts. After 30kts it stops. Tire is balanced, bearings are good, strut is serviced and I'm out of ideas on what to do to stop this shimmy.

Any thoughts are much appreciated! Thanks!

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7 hours ago, CAV Ice said:

Have a Columbia 400 with a nose wheel shimmy. It is very light below 20kts and increases to moderate between 25 and 28kts. After 30kts it stops. Tire is balanced, bearings are good, strut is serviced and I'm out of ideas on what to do to stop this shimmy.

Any thoughts are much appreciated! Thanks!


CAV,

We have a well respected Service center that wrote how to solve this problem for Mooneys…

The title of the bulletin is called ‘the eight second ride’  (a bull riding reference)

See if you can find the Don Maxwell Aviation site…. Where his writings are often available…

Briefly, The nose wheel is often responsible for shimmy for a couple of reasons…. Wear and proper over center alignment…

Do a search on the word plumb bob around here… there will be a picture showing the alignment of the nose wheel structure and the nose wheel…

For Mooneys with several thousand hours on them… OHing the nose gear is a short cut to getting back on the centerline…

 

Thanks for all your help over the years… hope this is helpful for you.

PP thoughts only, not a mechanic…

Best regards,

 -a-

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On 9/15/2021 at 3:56 PM, CAV Ice said:

Have a Columbia 400 with a nose wheel shimmy. It is very light below 20kts and increases to moderate between 25 and 28kts. After 30kts it stops. Tire is balanced, bearings are good, strut is serviced and I'm out of ideas on what to do to stop this shimmy.

Any thoughts are much appreciated! Thanks!

18 knots is about 20 mph, school zone speed in a car. If the shimmy is hardly noticeable below 20, I’d taxi below 20. How is it at 10 (running speed) or a 5 (very brisk walking speed)?

I can’t imagine taxiing a small airplane at 35 mph (30 knots). If you hit a pothole or bump at that speed a prop strike is almost a given.

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1 hour ago, LANCECASPER said:

18 knots is about 20 mph, school zone speed in a car. If the shimmy is hardly noticeable below 20, I’d taxi below 20. How is it at 10 (running speed) or a 5 (very brisk walking speed)?

I can’t imagine taxiing a small airplane at 35 mph (30 knots). If you hit a pothole or bump at that speed a prop strike is almost a given.

I agree on the taxi speed but he may be getting it on the roll out after landing.  This has happened to me a few times. It occurs very rarely but not fun when it does. 

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On 9/15/2021 at 3:56 PM, CAV Ice said:

Have a Columbia 400 with a nose wheel shimmy. It is very light below 20kts and increases to moderate between 25 and 28kts. After 30kts it stops. Tire is balanced, bearings are good, strut is serviced and I'm out of ideas on what to do to stop this shimmy.

Any thoughts are much appreciated! Thanks!

I think the most obvious way to get rid of the nose wheel shimmy on your Columbia 400 is to sell it and buy a Mooney....problem solved. :D

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While I know nothing about a Columbia, if it’s one of the nose wheels that aren’t steerable like a Cirrus or a Tiger etc, they often have a friction adjustment, if the friction is too lose, they will shimmy.

Van’s RV “A” model aircraft can wheel shimmy so bad that it collapses and has killed people, so treat nose wheel shimmy seriously.

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The one thing I notice about the Columbia design is there is not a lot of caster in the nose wheel. With a single tire not a lot of Marstand effect on the fork. I would change the tire and tube. True the rim while doing it as it could be bent. Check the axle for true, then verify the entire assembly runs true on the axle both laterally and radially. If all is good there I would turn my attention to the strut play within the tube. With as little caster, a little bit of play could create a lot of havoc down lower.

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